It has previously been proposed to construct a power amplifier as a switching amplifier. The output terminal of such an amplifier may be connected by way of two switching members, for example switching transistors, to either of two supply voltages, for example a positive and a negative voltage. The switching members are made alternately conducting with a relatively high switching frequency. By modulating the pulse-length of the output signal thus obtained, its mean value may be controlled in dependence on the input signal to the amplifier. In order to reduce the amplitude of the alternating voltage component caused by the switching, a filter, for example an LC filter, is arranged between the switching members and the output of the amplifier. The more efficient the filter is made, the smaller will be the band width of the amplifier, and in practice the filter is dimensioned so that a suitable compromise is obtained between the contrasting desires of an efficient filtering and a large band width. An amplifier of this kind has low losses but has the disadvantage that it is impossible simultaneously to obtain a large band width and a small ripple on the output signal.
The present invention aims to provide a power amplifier connected in which a small ripple of the output signal as well as a large band width may be obtained, and in which at the same time the losses are low.